<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>div样式</title>
    <style>
        /*#d1 .c1*/ div{
            border: 1px solid red;
            width: 60%;
            height: 500px;
            margin: auto;
        }
    </style>
</head>
<body>
    <div id = "d1" class = "c1">第一个div</div>
</body>
</html>